translate done: 20170924 Simulate System Loads.md

sources/tech/20170924 Simulate System Loads.md

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-translating by lujun9972
-Simulate System Loads
-======
-Sysadmins often need to discover how the performance of an application is affected when the system is under certain types of load. This means that an artificial load must be re-created. It is, of course, possible to install dedicated tools to do this but this option isn't always desirable or possible.
-
-Every Linux distribution comes with all the tools needed to create load. They are not as configurable as dedicated tools but they will always be present and you already know how to use them.
-
-### CPU
-
-The following command will generate a CPU load by compressing a stream of random data and then sending it to `/dev/null`:
-```
-cat /dev/urandom | gzip -9 > /dev/null
-
-```
-
-If you require a greater load or have a multi-core system simply keep compressing and decompressing the data as many times as you need e.g.:
-```
-cat /dev/urandom | gzip -9 | gzip -d | gzip -9 | gzip -d > /dev/null
-
-```
-
-Use `CTRL+C` to end the process.
-
-### RAM
-
-The following process will reduce the amount of free RAM. It does this by creating a file system in RAM and then writing files to it. You can use up as much RAM as you need to by simply writing more files.
-
-First, create a mount point then mount a `ramfs` filesystem there:
-```
-mkdir z
-mount -t ramfs ramfs z/
-
-```
-
-Then, use `dd` to create a file under that directory. Here a 128MB file is created:
-```
-dd if=/dev/zero of=z/file bs=1M count=128
-
-```
-
-The size of the file can be set by changing the following operands:
-
-  * **bs=** Block Size. This can be set to any number followed **B** for bytes, **K** for kilobytes, **M** for megabytes or **G** for gigabytes.
-  * **count=** The number of blocks to write.
-
-
-
-### Disk
-
-We will create disk I/O by firstly creating a file, and then use a for loop to repeatedly copy it.
-
-This command uses `dd` to generate a 1GB file of zeros:
-```
-dd if=/dev/zero of=loadfile bs=1M count=1024
-
-```
-
-The following command starts a for loop that runs 10 times. Each time it runs it will copy `loadfile` over `loadfile1`:
-```
-for i in {1..10}; do cp loadfile loadfile1; done
-
-```
-
-If you want it to run for a longer or shorter time change the second number in `{1..10}`.
-
-If you prefer the process to run forever until you kill it with `CTRL+C` use the following command:
-```
-while true; do cp loadfile loadfile1; done
-
-```
---------------------------------------------------------------------------------
-
-via: https://bash-prompt.net/guides/create-system-load/
-
-作者：[Elliot Cooper][a]
-译者：[lujun9972](https://github.com/lujun9972)
-校对：[校对者ID](https://github.com/校对者ID)
-
-本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
-
-[a]:https://bash-prompt.net

translated/tech/20170924 Simulate System Loads.md

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+模拟系统负载的方法
+======
+系统管理员通常需要探索在不同负载对应用性能的影响。这意味着必须要重复地人为创造负载。当然，你可以通过专门的工具来实现，但有时你可能不想也无法安装新工具。
+
+每个 Linux 发行版中都自带有创建负载的工具。他们不如专门的工具那么灵活但它们是现成的，而且无需专门学习。
+
+### CPU
+
+下面命令会创建 CPU 负荷，方法是通过压缩随机数据并将结果发送到 `/dev/null`：
+```
+cat /dev/urandom | gzip -9 > /dev/null
+
+```
+
+如果你想要更大的负荷，或者系统有多个核，那么只需要对数据进行压缩和解压就行了，像这样：
+```
+cat /dev/urandom | gzip -9 | gzip -d | gzip -9 | gzip -d > /dev/null
+
+```
+
+按下 `CTRL+C` 来暂停进程。
+
+### RAM
+
+下面命令会减少可用内存的总量。它是是通过在内存中创建文件系统然后往里面写文件来实现的。你可以使用任意多的内存，只需哟往里面写入更多的文件就行了。
+
+首先，创建一个挂载点，然后将 `ramfs` 文件系统挂载上去：
+```
+mkdir z
+mount -t ramfs ramfs z/
+
+```
+
+第二步，使用 `dd` 在该目录下创建文件。这里我们创建了一个 128M 的文件：
+```
+dd if=/dev/zero of=z/file bs=1M count=128
+
+```
+
+文件的大小可以通过下面这些操作符来修改：
+
+  + **bs=** 块大小。可以是任何数字后面接上 **B**( 表示字节 )，**K**( 表示 KB)，**M**( 表示 MB) 或者 **G**( 表示 GB)。
+  + **count=** 要写多少个块
+
+
+
+### Disk
+
+创建磁盘 I/O 的方法是先创建一个文件，然后使用 for 循环来不停地拷贝它。
+
+下面使用命令 `dd` 创建了一个充满零的 1G 大小的文件：
+```
+dd if=/dev/zero of=loadfile bs=1M count=1024
+
+```
+
+下面命令用 for 循环执行 10 次操作。每次都会拷贝 `loadfile` 来覆盖 `loadfile1`：
+```
+for i in {1..10}; do cp loadfile loadfile1; done
+
+```
+
+通过修改 `{1。.10}` 中的第二个参数来调整运行时间的长短。
+
+若你想要一直运行，直到按下 `CTRL+C` 来停止，则运行下面命令：
+```
+while true; do cp loadfile loadfile1; done
+
+```
+--------------------------------------------------------------------------------
+
+via: https://bash-prompt.net/guides/create-system-load/
+
+作者：[Elliot Cooper][a]
+译者：[lujun9972](https://github.com/lujun9972)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]:https://bash-prompt.net